java图片识别文字的方法

java文字识别程序的关键是寻找一个可以调用的OCR引擎。tesseract-ocr就是一个这样的OCR引擎，在1985年到1995年由HP实验室开发，现在在Google。tesseract-ocr 3.0发布，支持中文。不过tesseract-ocr 3.0不是图形化界面的客户端，别人写的FreeOCR图形化客户端还不支持导入新的 3.0 traineddata。但这标志着，现在有自由的中文OCR软件了。

java中使用tesseract-ocr3.01的步骤如下：

1.下载安装tesseract-ocr-setup-3.01-1.exe（3.0以上版本才增加了中文识别）

2.在安装向导中可以选择需要下载的语言包。

3.到网上搜索下载java图形处理所需的2个包：jai_imageio-1.1-alpha.jar，swingx-1.6.1.jar

4.java程序清单：

ImageIOHelper 类：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Locale;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.stream.ImageInputStream;
import javax.imageio.stream.ImageOutputStream;

import com.sun.media.imageio.plugins.tiff.TIFFImageWriteParam;

public class ImageIOHelper {

public static File createImage(File imageFile, String imageFormat) {
 File tempFile = null;
 try {
  Iterator readers = ImageIO.getImageReadersByFormatName(imageFormat);
  ImageReader reader = readers.next();

ImageInputStream iis = ImageIO.createImageInputStream(imageFile);
  reader.setInput(iis);
  //Read the stream metadata
  IIOMetadata streamMetadata = reader.getStreamMetadata();

//Set up the writeParam
  TIFFImageWriteParam tiffWriteParam = new TIFFImageWriteParam(Locale.CHINESE);
  tiffWriteParam.setCompressionMode(ImageWriteParam.MODE_DISABLED);

//Get tif writer and set output to file
  Iterator writers = ImageIO.getImageWritersByFormatName("tiff");
  ImageWriter writer = writers.next();

BufferedImage bi = reader.read(0);
  IIOImage image = new IIOImage(bi,null,reader.getImageMetadata(0));
  tempFile = tempImageFile(imageFile);
  ImageOutputStream ios = ImageIO.createImageOutputStream(tempFile);
  writer.setOutput(ios);
  writer.write(streamMetadata, image, tiffWriteParam);
  ios.close();

writer.dispose();
  reader.dispose();

} catch (IOException e) {
  e.printStackTrace();
 }
 return tempFile;
}

private static File tempImageFile(File imageFile) {
 String path = imageFile.getPath();
 StringBuffer strB = new StringBuffer(path);
 strB.insert(path.lastIndexOf('.'),0);
 return new File(strB.toString().replaceFirst("(?<=//.)(//w+)$", "tif"));
}

}

OCR 类：

package com.hhp.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.jdesktop.swingx.util.OS;

public class OCR {
private final String LANG_OPTION = "-l"; //英文字母小写l，并非数字1
private final String EOL = System.getProperty("line.separator");
private String tessPath = "C://Program Files (x86)//Tesseract-OCR";
//private String tessPath = new File("tesseract").getAbsolutePath();

public String recognizeText(File imageFile,String imageFormat)throws Exception{
 File tempImage = ImageIOHelper.createImage(imageFile,imageFormat);
 File outputFile = new File(imageFile.getParentFile(),"output");
 StringBuffer strB = new StringBuffer();
 List cmd = new ArrayList();
 if(OS.isWindowsXP()){
  cmd.add(tessPath+"//tesseract");
 }else if(OS.isLinux()){
  cmd.add("tesseract");
 }else{
  cmd.add(tessPath+"//tesseract");
 }
 cmd.add("");
 cmd.add(outputFile.getName());
 cmd.add(LANG_OPTION);
 cmd.add("chi_sim");
 //cmd.add("eng");

ProcessBuilder pb = new ProcessBuilder();
 pb.directory(imageFile.getParentFile());

cmd.set(1, tempImage.getName());
 pb.command(cmd);
 pb.redirectErrorStream(true);

Process process = pb.start();
 //tesseract.exe 1.jpg 1 -l chi_sim
 int w = process.waitFor();

//删除临时正在工作文件
 tempImage.delete();

if(w==0){
  BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(outputFile.getAbsolutePath()+".txt"),"UTF-8"));

String str;
  while((str = in.readLine())!=null){
   strB.append(str).append(EOL);
  }
  in.close();
 }else{
  String msg;
  switch(w){
   case 1:
    msg = "Errors accessing files.There may be spaces in your image's filename.";
    break;
   case 29:
    msg = "Cannot recongnize the image or its selected region.";
    break;
   case 31:
    msg = "Unsupported image format.";
    break;
   default:
    msg = "Errors occurred.";
  }
  tempImage.delete();
  throw new RuntimeException(msg);
 }
 new File(outputFile.getAbsolutePath()+".txt").delete();
 return strB.toString();
}
}

测试类TestOCR ：

import java.io.File;
import java.io.IOException;

import com.hhp.util.OCR;

public class OcrTest {

public static void main(String[] args) {
 String path = "C://temp//OCRcode//4.png";  
 System.out.println("ORC Test Begin......");
 try {  
  String valCode = new OCR().recognizeText(new File(path), "png");  
  System.out.println(valCode);  
 } catch (IOException e) {  
  e.printStackTrace();  
 } catch (Exception e) {
  e.printStackTrace();
 }  
 System.out.println("ORC Test End......");
}

}

经过测试，tesseract-ocr 3.01的文字识别率很高，对于网站中常见的验证码识别率也很高。

来源：https://blog.csdn.net/tiny_lxf/article/details/78533485